**剧透警告**： 教程 - 用户指南中的内容有：

* 对来自不同地方的参数进行声明，如：**请求头**、**cookies**、**form 表单**以及**上传的文件**。
* 如何设置**校验约束**如 `maximum_length` 或者 `regex`。
* 一个强大并易于使用的 **<abbr title="也被称为 components, resources, providers, services, injectables">依赖注入</abbr>** 系统。
* 安全性和身份验证，包括通过 **JWT 令牌**和 **HTTP 基本身份认证**来支持 **OAuth2**。
* 更进阶（但同样简单）的技巧来声明 **多层嵌套 JSON 模型** （借助 Pydantic）。
* 许多额外功能（归功于 Starlette）比如：
    * **WebSockets**

	m.respWait = out
}

// RequestStream will send a single payload request and stream back results.
// 'requests' can be nil, in which case only req is sent as input.
// It will however take less resources.
func (m *muxClient) RequestStream(h HandlerID, payload []byte, requests chan []byte, responses chan Response) (*Stream, error) {
	if m.init {
		return nil, errors.New("mux client already used")
	}

### Dependency Injection { #dependency-injection }

FastAPI enthält ein extrem einfach zu verwendendes, aber extrem mächtiges <abbr title='auch bekannt als „Komponenten“, „Resourcen“, „Dienste“, „Dienstanbieter“'><strong>Dependency Injection</strong></abbr> System.

* Selbst Abhängigkeiten können Abhängigkeiten haben, woraus eine Hierarchie oder ein **„Graph“ von Abhängigkeiten** entsteht.

 * {@link PriorityQueue} and supplies blocking retrieval operations. While this queue is logically
 * unbounded, attempted additions may fail due to resource exhaustion (causing {@code
 * OutOfMemoryError}). This class does not permit {@code null} elements. A priority queue relying on
 * {@linkplain Comparable natural ordering} also does not permit insertion of non-comparable objects

  feedback for that case. However, when offline mode is declared, nothing
  earmarked as remote should be accessed, regardless of whether it is actually
  a physically local resource.

  NOTE: One side effect of this design change is that all offline-mode code can
  be isolated to maven-core, maven-plugin-descriptor, and [possibly]
  maven-artifact. Usage of maven-wagon will be determined by an offline-aware

      }

      /**
       * Returns an input stream containing one or more certificate PEM files. This implementation just
       * embeds the PEM files in Java strings; most applications will instead read this from a resource
       * file that gets bundled with the application.
       */
      private fun trustedCertificatesInputStream(): InputStream {
        ... // Full source omitted. See sample.
      }

    * Cookies, 等等。

加上来自 Starlette（包括 **session cookie**）的所有安全特性。

所有的这些都是可复用的工具和组件，可以轻松与你的系统，数据仓库，关系型以及 NoSQL 数据库等等集成。



### 依赖注入

FastAPI 有一个使用非常简单，但是非常强大的<abbr title='也叫做 "components", "resources", "services", "providers"'><strong>依赖注入</strong></abbr>系统。

* 甚至依赖也可以有依赖，创建一个层级或者**“图”依赖**。
* 所有**自动化处理**都由框架完成。
* 所有的依赖关系都可以从请求中获取数据，并且**增加了路径操作**约束和自动文档生成。
* 即使在依赖项中被定义的*路径操作* 也会**自动验证**。

You could need to tell the client that:

* The client doesn't have enough privileges for that operation.
* The client doesn't have access to that resource.
* The item the client was trying to access doesn't exist.
* etc.

In these cases, you would normally return an **HTTP status code** in the range of **400** (from 400 to 499).

  /**
   * <a href="https://en.wikipedia.org/wiki/RDF/XML">RDF/XML</a> documents, which are XML
   * serializations of <a
   * href="https://en.wikipedia.org/wiki/Resource_Description_Framework">Resource Description
   * Framework</a> graphs.
   *
   * @since 14.0
   */
  public static final MediaType RDF_XML_UTF_8 = createConstantUtf8(APPLICATION_TYPE, "rdf+xml");

  // without the reference to unlimited queues.
  /**
   * Returns the number of additional elements that this queue can ideally (in the absence of memory
   * or resource constraints) accept without blocking. This is always equal to the initial capacity
   * of this queue less the current {@code size} of this queue.
   *